Insulating material



Patented May 17, 1927.

UNITED STATES v. PATENT OFFICE.

ARCHIE R. KEMP, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

INSULATING MATERIAL.

No Drawing.

This invention relates to insulated cables and particularly to a plasticmaterial for use in joining or covering sections of such cables.

\Vhen two sections of cable comprising an electric conductor coveredwith a vulcanized sheathing are spliced together to provide amechanically and electrically continuous conductor, it is necessary thatthe splice be provided with a suitable insulating covering. It is alsosometimes necessary to cover a portion of such conductor which maybecome exposed due to the removal of the associated vulcanizedsheathing, with a substitute covering. Since in such cases the coveringmust firmly unite with the insulation of the remainder of the cable, itis desirable that the covering be readily adhesive and he of such acharacter that it may be vulcanized within a short period of timewithout deleteriously affecting the previously vulcanized sheathingadjacent thereto.

It is the principal object of this invention to enable the covering ofsplices in an insulated cable with a plastic compound which may berapidly vulcanized without injuring the cable insulation and which formsa coating firmly united with the vulcanized coating on the remainder ofthe cable, the joint thus formed having a permanently high insulationresistance.

To attain this object, the invention contemplates a plastic materialwhich may be readily fashioned about the conductor splice, which may berapidly vulcanized without inj uring the insulation of the adjacentcable and which will unite firmly with the cable insulation and be ofsufiicient toughness to withstand any mechanical injury to which it maybe subjected in service.

This invention is applicable to the general forms of rubber insulatedcable. In the manufacture of such an insulated cable, a thin layer ofsubstantially pure gum rubber is formed around the conductor and plasticvulcanizable material is then extruded over the previously appliedrubber and the core sheathing is vulcanized in any suitable manner.IVhen it is desired to cover a splice, or an otherwise exposed portionof such conductor, it is necessary to employ a material having thecharacteristics referred to above. A plastic material which has beenSerial No. 673,822.

found to give very satisfactory results under the most severe conditionsconsists essentially of the following ingredients and in the proportionsnamed:

These ingredients are mixed intimately according to the usual well knownmethods. The litharge acts as an accelerator and the comparatively largepercentage which is used makes it possible to obtain the desired degreeof vulcanization in a very short period of time. It is thus possible notonly to vulcanize the plastic material about the splice without injuringthe vulcanized covering adjacent thereto but also to quickly completethe vulcanizing process. This is of particular importance in connectionwith the laying of submarine cables which are necessarily spliced aboardship.

\Vhile the formula given above under usual conditions gives the mostsatisfactory results, the proportions may be varied somewhat to suitparticular conditions.

Various methods may be employed for fashioning this plastic material onthe spliced conductor but the method preferred is disclosed in detail inmy Patent No. 1,586,811 granted on June 1, 1926.

As a result of exhaustive testsit has been demonstrated that cablesplices insulated with a jacket of plastic material of the typedescribed are capable of withstanding the most severe conditions towhich they are apt to be subjected in service and are satisfactory t'romthe standpoint of insulation resistance.

\Vhat is claimed is:

A jointing compound for rubber insulated cables comprising the followingingredients in approximately the proportions named, rubber 40%, zincoxide 34%, litharge 20%,

sulphur 4%, parafiine 2%.

In witness whereof, I hereunto subscribe my name this 15th day ofOctober A. D.,

ARCHIE R. KEMP.

